I have added the Austrians, Cherokee, and Ethiopians to my epic game, and so far it has worked out good. Cherokee and Ethiopian civs were put together by me yet Austria came with the game as an alternative to the Sumerians.
If you shall replace any civilization with Austria, it should be Sumeria for these reasons:
1. Very little is known about the Sumerians
2. The Enkidu Warrior is a made up unit
3. Cities names are similar to Babylon's
4. Inhabited same region as Babylon
5. Traits match China very well
So this is what I did.. I changed Sumeria to Austria in the editor, I changed China's traits to Sumeria's and gave Austria China's old traits. I added the units of Hussar and Grenzer to the game. I first had the Hussar be Austria's UU but then I realized that Hussars were used in many European countries so then I made it generic and weaker than the Cavalry, and then I added the Napoleon Gaurd unit from the Napoleonic Europe conquest and renamed it Grenzer and gave that to Austria. To make the Grenzer more historically accurate I changed the Musketman to Arquebusier and used the Napoleonic Musketman as a Musketman.
I know you can't do much of what I said, but I'm just giving you some hints. In fact, I feel like releasing a basic Austria mod.
I had also given step by step instructions on how to add Austria to the game with the exact pediaicons.txt and civilopedia.txt scripts but I can't find that thread.
Have fun.